Design and development of an experimental setup for nanofinishing of exhaust valves using magnetorheological finishing to enhance functional performance

Abstract

Exhaust valves in high-performance and racing engines require ultra-smooth surfaces to improve durability and operational efficiency. This study investigates the application of Magnetorheological (MR) polishing for finishing exhaust valve seats. MR fluid, consisting of micron-sized magnetic particles suspended in a carrier liquid, forms a semi-solid structure under a magnetic field, enabling precise surface finishing. An in-house experimental setup was developed, and various magnet configurations were tested to optimize the polishing zone. Computational investigations were conducted to analyze magnetic field distribution for 2-bar, 3-bar, 4-bar, and 5-bar magnet systems, with results validated using a Gauss-meter. Unlike prior MR polishing studies that focused mainly on optical or biomedical components, our work emphasizes automotive engine applications and demonstrates the optimization of a 4-magnet system to achieve uniform magnetic field distribution. The novelty lies in developing a cost-effective, adaptable, and reproducible MR polishing arrangement tailored for curved valve geometries, while addressing reproducibility through detailed experimental parameters. The primary objective was to optimize process parameters for MR polishing. Under optimal conditions—spindle speed of 750 RPM, stand-off distance of 1.5 mm, and polishing time of 17.5 min—the surface roughness (R<inf>a</inf>) improved significantly from 0.613 ?m to 0.115 ?m. Measurements were performed using a 3D profilometer. Further surface characterization via Atomic Force Microscopy (AFM) showed a reduction in surface asperities, while Field Emission Scanning Electron Microscopy (FE-SEM) revealed fewer surface scratches. These results confirm the potential of MR polishing as an effective technique for enhancing the surface finish of critical engine components. © The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature 2025.